Concentric line coupling



Jan. 7, 1941. -J. G. CHAFFEE x2,227,487

CONCENTRIC LINE COUPLING Filed Sept. 16, 1939 //vl/EN7UR J. G. CHAFFEEimza' Patented Jan. 7, 1941 UNITED STATES PATENT OFFICE CONCENTRIC LINECOUPLING Application September 16, 1939, Serial No. 295,219

4 Claims. (Cl. 178-44) This invention relates to improved arrangementsfor coupling concentric transmission lines with apparatus in ultra-shortwave systems.

At ultra-high frequencies thephysical dimensions of tuning capacitiesand coupling coils become very small and the use of flexible leads topermit variation of the coupling between associated circuits is commonlyfound to be unsatisfactory since changes in the physical arrangement ofthe flexible leads incident to coupling adjustments are usuallyaccompanied by undesired changes of appreciable magnitude in theelectrical constants of the circuits in whichleads are included. Thearrangements of the present invention contemplate the use of a collarfitting over the associated concentric line and adapted both to turn andto slide thereon. The collar carries one or several turns of anelectrical conductor having an inductance of suitable magnitude. Acircular plate is supported by the aforesaid turn or turns normally toand concentrically with the axis of the coaxial conductor.

A second circular plate is similarly supported by the inner conductor ofthe concentric line, the two plates forming a capacity, variable withinappropriate limits by sliding the collar longitudinally on the outerconductor of the concentric line but unaffected by rotation of thecollar on the outer. conductor.

Coupling to apparatus to be associated with the concentric line iseffected inductively between the above-mentioned turn or turns and asimilar, but stationary, inductive circuit embodied in the input (oroutput) circuit of the apparatus. Turning the above-mentioned collar onthe outer concentric conductor will obviously serve to vary theinductive coupling between the apparatus and the line but will notchange the capacity between the above-mentioned pair of concentriccircular plates. On the other hand, if the coupling and input circuitcoils are so positioned that their axes substantially coincide, slidingthe above-mentioned collar on the outer concentric conductor so as tovary the tuning of the coupling circuit will have an effect upon thecoupling small compared with that resulting from its rotation. Thussubstantially independent control of two important parameters of thecoupling arrangement is therefore afforded without the use of flexibleleads in the usual sense of the term. As will appear more fullyhereinafter a symmetrical arrangement of the components of the couplingis frequently found desirable.

,' The principles of the invention will become more apparent inconnection with the following detailed description of illustrativeembodiments together with the accompanying drawing in which:

Fig. 1 shows a preferred symmetrical form of structure of the inventionas applied to the end of the associated concentric line;

Fig. 2A shows in electrical schematic form the complete couplingarrangement contemplated in the invention;

Fig. 2B shows in diagrammatic form the coupling arrangement of theinvention employed to couple a concentric line to a balanced circuit;

Fig. 2Cshows in diagrammatic form the cou pling arrangement of theinvention employed to couple a concentric line to an unbalanced circuit;

Fig. 3 shows an unsymmetrical form of structure of the invention forapplication to the end of an associated concentric line; and

Fig. 4 shows in electrical schematic form a concentric line coupled toan external circuit as contemplated in connection with the structure ofFi 3.

In more detail, in Fig. 1 concentric line com-r prising inner conductorl2 and outer conductor H is provided with a collar l4 arranged both toslide longitudinally and to rotate on outer con ductor l I. Two helicalturns of rigid conducting material l5 and H are supported by collar I4,their outer ends being fastened by soldering, welding, or otherconvenient method, to collar [4' at diametrically opposite positionsthereon.

The inner ends of turns l5 and I! are joined and at the mid-pointtherebetween, they support a short conductor l6 having at its left end adisc I8 of conducting material. Disc l8 should be supported in a planeperpendicular to the axis of concentric line H, l2 and its center shouldbe on the axis. A second disc 20 is supported by inner conductor 12 in aplane normal to the axis of concentric pair I I, I2 and concentrictherewith.

Turns l5 and I! are wound in opposite directions since the currentsthrough them at any particular instant will flow in opposite directions.The virtue of the particular arrangement shown lies in its symmetry, itstendency to more evenly distribute the current at the end of outerconductor II, and its mechanical rigidity. A stop 24 which may comprisea collar or shoulder of any convenient form is preferably fastened onouter conductor II and so positioned as to pre vent plate l8 from beingbrought into physical contact with plate 20.

By placing a second inductive loop or circuit comprising one or moreturns, similar to turns l5 and H, in the neighborhood of the latter,inductive coupling to an external circuit as illustrated in theschematic diagram of Fig. 2A may obviously be effected and the degree ofcoupling may be adjusted by rotating collar 14.

In Fig. 2A, inductances 25 and 28 are oppositely wound coils, or singleturns, arranged and supported in a manner similar to that of turns l5and I! of Fig. 1, capacity 32 is formed between two plates positionedsubstantially as are plates I8 and 20 of Fig. 1 and is adjusted as inthe case illustrated by Fig. 1 by sliding a collar longitudinally alongthe outer conductor of the concentric pair until the circuit is tuned asdesired. Inductance of Fig. 2A represents an external coil or loopinductively coupled with members 26and 28 and condenser 34 represents ameans of tuning the external circuit as desired.

In Fig. 213, it is diagrammatically shown how an external circuit whichis balanced to ground may be conveniently coupled to a concentric lineby means employing the structure of Fig. 1. In Fig. 2B capacity 42 is,of course, that between plates l3 and 2i] of Fig. 1 and is'adjusted bysliding collar is to tune with inductances l5 and IT to the desiredresonant point. It is preferable, as mentioned above, that the system beso proportioned that the normal operating adjustments desired will notcause the centers of coils l5 and ll to depart a substantial distancefrom the common axis of coils 3t and 38.

In the balanced portion of the circuit shown to the right in Fig. 2Bbalanced inductors and 33 are placed so as to symmetrically couple toinductors I 5 and i1 between them. The midpoint of the circuit betweeninductors 35 and 33 is grounded. Variable capacity 40 is added to permitappropriate tuning of the external circuit.

In Fig. 20 another diagrammatic representation of coupling a concentricline with an external circuit is given. The arrangement of Fig. 2C lacksthe electrical symmetry of that of Fig. 2B and is preferably used onlywhen no severe balance requirements are to be satisfied. It is, ofcourse, appropriate for use where external circuit comprising inductor44 and capacity 45 represents an unbalanced circuit. For the latter caseit is also possible to replace inductors l5 and H by a single inductoras as shown in Fig. 3. The equivalent electrical circuit may then berepresented as shown in Fig. 4, inductor 52 and capacitance 54',representing an unbalanced circult and capacity 5t and inductor d8represent a coupling arrangement similar to that of Fig. 1 but with asingle inductor .8 employed in place of inductors I5 and I! of'Fig. 1.Coils A8 and 52 are, of course, to be positioned mechanically asindicated for the two inductive elements of the diagrammaticrepresentation of Fig. 2C.

In any of the arrangements shown the preferred procedure in makingadjustments is as follows: With a value of coupling well below thecritical value, tuning of the coupling circuit is first effected bysliding the collar supporting the coupling coil so as to vary thecapacity between the plates corresponding to plates l3 and Zil ofFig. 1. Then the coupling is increased by rotating the collar until amaximum transfer of energy takes place between the transmission line andthe associated circuit.

Numerous other arrangements embodying the principles of the inventionwill occur to those skilled in the art. No attempt has here been made toexhaustively cover all applications of the principles of the invention.

The scope of the invention is defined in the following claims.

What is claimed is:

1. Means for coupling a coaxial line with an external circuit comprisinga collar of conducting material fitting the end of the outer conductorof the coaxial line, the position of said collar on said conductor beingadjustable by sliding longitudinally and by turning with respect to saidconductor, an inductive element supported on said collar, said inductiveelement comprising a conductor coiled about an axis at right angles, tothe axis of said coaxial line, a condenser one plate of which issupported by the end of the inner conductor of said coaxial line and theother plate of which is supported by said inductive element and a fixedexternal circuit said external circuit including a second inductiveelement comprising a second conductor coiled about an axis so positionedthat it will coincide with the axis of the first-mentioned inductiveelement for a particular position of said collar upon the said outerconductor inductively coupled with said inductive element.

2. In combination, a coaxial line, a collar fitting the end of the outerconductor of said line and adapted to slide and turn thereon, aninductive element supported on said collar said element comprising aconductor coiled about an axis substantially at right angles to the axisof said coaxial line, a capacity formed by two circular plates one ofsaid plates being supported on the end of the inner conductor of saidcoaxial line, the other of said plates being supported by said inductiveelement, both of said plates being normal to and having a common axiswith said line and an external circuit said circuit including a secondinductive element comprising a second conductor coiled about an axiswhich is in substantially the same plane as the axis about whichthefirst-menticned conductor is coiled whereby said external circuit maybe inductively coupled with said inductive element.

3. Means for coupling a coaxial line with a balanced circuit comprisinga collar arranged to slide and turn on the end of said line, a balancedinductive element the outer ends of said element being supported by saidcollar at diametrically opposite positions on said collar the electricalcenter of said balanced inductive element being coincident with thelongitudinal axis of said collar, the two halves of said element beingwound inversely with respect to each other, a capacitance formed by twocircular plates, one of said plates being supported by the innerconductor of said line, the other of said plates being supported by saidinductive element and electrically connected to the electrical centerthereof, both of said plates being supported normally to andconcentrically with respect to the axis of saidline and an externalcircuit coupled inductively and said two coils and the translation ofthe said one of said coils is effective to change the capacity of saidcondenser with a relatively small change in the coupling between saidcoils.

JOSEPH G. CHAFFEE.

